1. Field of the Invention
The present invention relates to a method for producing offset surfaces and offset solids. More particularly, the invention relates to an offset curved surface production method and an offset solid production method in data production of three-dimensional data processing apparatus. The method may be applied-for example to a solid producing apparatus for defining a complex solid.
2. Description of the Related Art
A recent trend is execution of structural analysis or of machining based on data through a definition of three-dimensional solid using the three dimensional CAD system on a computer. A high performance data defining capability is required for the three-dimensional CAD system to support it. There are diverse input methods expected.
The three-dimensional CAD system handles various input data. Generally, the most frequent chance of input is a solid with an identical sectional thickness. An offset solid production method is very effective to input such a solid. Most of three dimensional CAD's lack this function, so that the process is usually ended either with only formation of outer form or with rough formation of inner form.
This is because it is too difficult to make an offset solid by combining offset surfaces for respective surfaces. Japanese Unexamined Patent Publication No. 2-51779 describes an "offset curve production method", by which only a curve can be offset. R. T. Farouki, "Exact offset procedures for simple solids," Computer Aided Geometric Design 2, pages 257-279, 1985, concerns a method for producing an offset solid to a simple solid such as cylinder, cone, etc. using its properties, and also teaches the difficulties of process for more complex solid.